Toxic unit , definition

The humic/organic matter coatings of different solid phases (i. e., SPm /SP0M), such as soils, sediments, suspended solids, colloids, and biocolloids/biosolids, interact with organic pollutants in aqueous systems in various ways. Adsorption is an important interaction mode. The reversibility and/or irreversibility of the adsorption processes is of major importance. The question whether the bound residues of pollutants are to be considered definitely inactivated has been the focus of extensive research. This question was posed as follows. Have the adsorbed pollutants become common components incorporated into the humic polymer coating of solid phases (i. e., being absorbed), or are they only momentarily inactivated in reversibly bound forms thus representing a possible source of pollution by a time-delayed release of toxic units ... 

Which effect assessment method should be applied in a particular situation depends on the nature of the mixture problem at hand. Because the diversity in assessment methods is large, it is important to clearly describe the problem. For example, derivation of a safe level for a proposed industrial mixture emission requires a different approach than the prioritization of a number of sites contaminated with mixtures. The former problem requires the assessment of realistic risks, for example, by the application of a suite of fate, exposure, and effect models, whereas the application of a simple consistent method suffices to address the latter problem, for example, a toxic unit approach. A successful and efficient assessment procedure thus starts with an unambiguous definition of the mixture problem at hand. The problem definition consists of the assessment motive, the regulatory context, the aim of the assessment, and a structured or stepwise approach to realize the aim. Elaboration of the problem definition is an iterative process (Figure 5.1) that strongly depends on factors such as resources, methods, data availability, desired level of accuracy, and results of previous studies. 

Soon after the Bhopal accident, the government of India promised to conduct a comprehensive study on the acute and long-term effects of exposme to MIC. The Indian Council of Medical Research (ICMR) released approximately 2 million for research a cohort of 80,021 gas-exposed people and 15,931 controls were registered, but only 16,8 exposed subjects and 5,741 controls could be contacted in 2010 (Sharma, 2013). Researchers were not recruited to study all aspects of toxicity. No definite criteria were set to make a quantitative assessment of the exposure to MIC the best estimate has remained the distance from the Union Carbide factory (Dhara et al., 2002). A number of laboratories in the United States and United Kingdom initiated research on MIC (Environmental Health Perspective, 1987), but their interest faded quickly. The twentieth anniversary of the disaster drew the attention of the media, but not of researchers. 

Threshold lamit Value - The term refers to toxicity by inhalation. The abbreviation used is TLV. The TLV is usually expressed in units of parts per million (ppm) - i.e., the parts of vapor (gas) per million parts of contaminated air by volume at 25 °C (77°F) and atmospheric pressure. For chemicals that form a fine mist or dust, the concentration is given in milligrams per cubic meter (mg/m ). The TLV is defined as the concentration of the chemical in air that can be breathed for five consecutive eight-hour workdays (i.e., 40 hours per week) by most people without suffering adverse health effiects. This is the definition given by the American Conference of Governmental Industrial Hygienists. 

The unitized package protocol established similar numerical limits, but then added the definition of what constitutes a toxic amount of product for a 25 lb child. For aspirin, eight tablets were determined to be the realistic package failure criteria. The failure... 

First, of all, I would like to clarify the term "new chemicals." I am referring to the TSCA definition as those chemicals not listed on the TSCA Chemical Substance Inventory and maintained on a daily basis by the Office of Toxic Substances within EPA. This is a list of all commercial chemicals - some 55,000 in all - produced in or imported into the United States during the period of 1975 through 1979. My talk this afternoon will not cover the thousands of formula changes in mixtures of chemicals which occur almost daily as industry tries to meet changing market demands. 

Dose In the context of chemicals, the temi dose means the amount, quantity, or portion of the chemical exposed to or applied to the target (e.g., a human being). It may also refer to a consistent measure used in toxicological testing to determine acute and chronic toxicities. An alternate definition is die amount of ionizing radiation energy absorbed per unit mass of irradiated material at a specific location, such as a part of die human body, measured in REMS, or an inanimate body, measured in rads. 

In practice, there will sometimes be situations for which saltwater toxicity data are not available. In these situations, it may be deemed necessary to use freshwater data in lieu of data for marine species. However, several regulatory authorities (e.g., Australia, Canada, and the United States) would not extrapolate from freshwater data to set a definitive marine EQS. Based on acute SSDs, Wheeler et al. (2002) concluded that it is possible to use freshwater toxicity data to extrapolate to saltwater effects by applying an appropriate assessment factor. However, they did not propose a value for this factor moreover, looking in detail at their results (see Section 4.6.1), this extrapolation could be overprotective in some cases. 

Just as qualitative judgments of toxicity are made using a reference point on the metabolism rate-concentration relationship, quantitative evaluation of toxicity is also made with respect to a reference point. It would seem that the definition of the point of reference for quantitative evaluation should be more exact than that used for qualitative judgment. Unfortunately, this is not the case for waste treatment system studies. In virtually all quantitative toxicity studies, the performance of units containing added quantities of the substance under study is compared with the performance of a control unit. Invariably, the control unit is one which exhibits satisfactory biological activity and to which none of the substance under study has been added. Very rarely is the concentration of the substance under study established or fixed in the control. 

The frequency of such reactions is about 1-3 reactions per 1000 intramuscular injections of penicillin G procaine, the usual dose being about 0.6-1.2 million units (175,213,225-227). Eight of 920 patients with venereal diseases had a definite toxic-like reaction with a dose of 4.8 million units of penicillin G procaine, corresponding to about one in 120 patients (228). In a series of 7700 intramuscular injections with only 400 000 units of penicillin G procaine, there was not one episode (221). 

The United States of America in 1998 announced the Chemical Right-to-Know (RTK) Initiative46 which was the US government response to an Environmental Protection Agency (EPA) study that found that very little basic toxicity information is publicly available on most of the HPV chemicals made and used in the USA. It should be noted that the US definition of UPV chemicals is different from that used in the rest of the world, as the US definition is a chemical produced in or imported into the US A in amounts... 

The major reason for the exclusion of chemicals that are toxic to plants from the CWC s definition lies in the United States usage of defoliants during the Vietnam War and its refusal during the CWC negotiations to have this included in the definition. 

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